This application is related to U.S. provisional application No. 61/716,274, filed Oct. 19, 2012, entitled “APPARATUS FOR ELECTRICALLY RETRACTING A DOOR LATCH”, naming Scott G. Morstatt, Jeffrey Sharps, and Anthony Benitez as the inventors. The contents of the provisional application are incorporated herein by reference in their entirety, and the benefit of the filing date of the provisional application is hereby claimed for all purposes that are legally served by such claim for the benefit of the filing date.
An apparatus is shown and described for electromechanical retraction of a door latch, including a dogging mechanism for holding the door latch in a retracted position and, more particularly, an apparatus for electromechanical door latch retraction and dogging which uses less power in the retracted and dogged state.
An exit device for a door generally includes a frame or housing secured across a door face and substantially spanning the width of the door. A touch bar, sometimes referred to as a “panic bar” or “push bar”, is movably mounted to the frame. The touch bar is mechanically linked to a latch mechanism, including a door latch which is movably mounted on the frame adjacent to a free edge of the door. Depressing the touch bar in the frame and toward the door translates the mechanical linkage for actuating the latch mechanism in order to retract the door latch, which may be a rim latch with a latch bolt or vertical rods with ceiling and floor latches, so that the door can be opened.
It is known to fix or “dog” an exit device in order to maintain an unlocked condition. Typically, dogging requires that the touch bar be held in its depressed or actuated position and prevented from returning to its outward position such that the door latch remains in a retracted position. Dogging mechanisms are useful to facilitate entry and exit through the door during heavy usage times, such as at the start and end of a work shift and during emergencies, or when there is no latch actuator on the outside of the door to gain entry.
Manually or electrically operated dogging mechanisms are available for holding the touch bar in the depressed position or keeping the latch bolt retracted. For example, an electrically operated exit device may use a solenoid to dog the touch bar in its depressed position. The plunger of the solenoid may also be operatively coupled to the door latch for moving the latch bolt from its projected position to its retracted position and holding the latch bolt in its retracted position, whether or not the touch bar is electrically dogged. In either type of exit device, the solenoid must provide a substantial force to retract and hold the touch bar or door latch, especially to overcome initial friction. Consequently, a relatively high operating current is required to reliably retract the touch bar or the latch bolt, and to dog the touch bar or latch bolt in the retracted position.
For the foregoing reasons, there is a need for a new apparatus for use in an electromechanically operated exit device, including a solenoid for retracting a latch bolt, and which will require significantly less power for maintaining the solenoid plunger, and therefore the latch bolt, in the retracted position until the latch bolt is released. The new apparatus should include a dogging assembly for an exit device for holding the latch bolt in the retracted position.